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Physics Seminar

Coherent optics with spins in semiconductor nanostructures

Speaker: Ilya Akimov (TU Dortmund)
Date: Wednesday 24 November 2021
Time: 15:00
Venue: Zoom

Coherent optical response provides rich information about the energy structure and dynamical properties of the studied system and can be used for applications in quantum memories where light-matter interaction is exploited to store and retrieve optical fields in the form of photon echoes. Excitons in semiconductor nanostructures can be excited resonantly by sub-ps optical pulses on a very short timescales enabling access to large bandwidths but unavoidably leading to short radiative lifetime, which imposes limitation for optical storage time. Using the spin degrees of freedom it is possible to extend the timescale of coherent optical response by several orders of magnitude and to explore the fascinating field of coherent optics with spins. In the talk I show that the long-living spin-dependent photon echo from resident carriers can be observed in self-assembled InGaAs quantum dots despite the strong inhomogeneous broadening of optical transitions. We demonstrate that such spin dependent photon echoes can be used as an optical probe to study the transport of charge carriers. For instance, we measure the signal decay in quantum wells and obtain the hoping times of resident electrons between the localized sites. In the last part I will discuss Rabi oscillations and their impact on optical control of the photon echo timing. There, the dephasing and rephasing of excitons in quantum dots are controlled by an additional optical 2π pulse.

Short bio: Ilya Akimov graduated from State Electrotechnical University, St. Petersburg in 1997 and obatined PhD degree in physics in 2000 at Ioffe Physical Technical Institute, St. Petersburg, Russia. Between 2001 and 2006, he worked as a Postdoc at Photonics Chair in Humboldt University in Berlin, Germany and as a research assistant at PennState University in USA. In 2007, he joined Experimental Physics 2 in TU Dortmund, where he has been a professor since 2019. His research interest includes spin-related and magneto-optical phenomena in semiconductor nanostructures and magnetic materials using transient coherent optical spectroscopy.